Technical Abstract:
This study will quantify the effectiveness of best management practice (BMP) in enhancing the treatment of stormwater runoff. By combining treatment mechanisms in series rather than using a single method of treatment for stormwater, the overall levels and reliability of pollutant removal can be improved. The enhanced BMP or BMP in series will include an alum treatment facility in addition to wetland cells to treat stormwater runoff and baseflow from the 5,800-acre southern portion of the 6,289-acre Eastside Canal Watershed in Plant City, Florida. The injection of alum, Al(SO4)2 .12H2O into a stormwater flow has been documented elsewhere for the control of phosphorus and, to a lesser extent, nitrogen. Alum also exhibits excellent treatment efficiencies for other pollutants (suspended solids, heavy metals, fecal coliforms, etc.) found in stormwater. This type of pollutant removal occurs naturally when stormwater flows over saturated fine mineral soils that typically have higher concentrations of aluminum. The design of the wetland treatment Includes treatment cells planted with a variety of emergent plants emphasizing persistent species such as iris, rush, and cordgrass. These species are known to enhance nutrient uptake. The overall design plan of the wetland cells will ensure that maintenance activities can be carried out efficiently within the cells to allow periodic removal of aged plants to further enhance the nutrient removal efficiency of the cells. Very little information has been published for BMP in series and there is no published value for the proposed enhanced wetland system. The actual load reductions may be significant because alum will be used in conjunction with a wetland system. The BMP effectiveness evaluation phase will improve future estimates for nutrient load reductions resulting in better future management decisions.